System and method for passive remote detection of gas plumes

Abstract

The present invention includes systems and methods for quantitative and qualitative imaging of gases, vapors, fumes, and the like. In one embodiment, the system uses a moving, or a rotating filter for alternately capturing on-line and off-line images of a scene that potentially includes the target gas of interest. The moving, or rotating filter includes at least two filter segments for transmitting (a) wavelengths corresponding to a spectroscopic absorption feature for on-line elements of the target gas, and (b) nearby wavelengths not corresponding to a spectroscopic absorption feature for off-line elements of the target gas. An image processor executes an algorithm for transforming the collected on-line and off-line data, corresponding to different pixels in the imaging array, into an image map of path-integrated concentration, or concentration path lengths (CPLs). The systems and methods of the invention do not use active light sources to illuminate the target gas. Instead, imaging and processing is done entirely using passive received energy from the target gas.

Description

FIELD OF THE INVENTION[0001]The present invention relates, in general, to passive detection, imaging and measurement of gas plumes. More specifically, the present invention is directed to passive detection and measurement of gas plumes employing two or more filters together with an infrared imaging focal plane array (FPA) and a processing unit. The two filters may be moving or stationary filters, or may be an etalon configured to pass light that is in phase and out of phase having periodic spectral features of a predetermined gas or multiple gases.BACKGROUND OF THE INVENTION[0002]Gas species typically have unique spectral features in the midwave (3-5 micron) and / or the longwave (8-14 micron) infrared (IR) regions of the electromagnetic spectrum. Whether the spectral features manifest themselves as an emission spectrum or an absorption spectrum depends upon the temperature of the gas relative to its background. If the gas is cooler than the background, the gas exhibits an absorption ...

AI Technical Summary

Benefits of technology

The present invention provides a device that can detect and measure multiple gases simultaneously by using a filter with multiple sets of on-line and off-line filter segments. The device can have a longer integration time to compensate for the shorter duration of exposure of each filter segment on the filter wheel. Additionally, the device can use two separate FPA sensors, one for each filter, which eliminates moving parts and decreases the integration time necessary to collect sufficient data. The two resulting images that correspond to the two separate FPA sensors are registered to each other, and further processing can be applied.

Problems solved by technology

DIAL systems, however, tend to be relatively expensive and require active illumination.

Active illumination is undesirable, since the source of the illumination may potentially be detected by an enemy.

The aforementioned systems, whether they include a gas cell or not, are relatively insensitive.

Thus, these systems include active sources of illumination, which are undesirable.

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